Quantifying the effects of in-stream habitat structure and discharge on leaf retention: implications for stream restoration

Koljonen, Saija; Louhi, Pauliina; Mäki‐Petäys, Aki; Huusko, Ari; Muotka, Timo

doi:10.1899/11-173.1

Cited by 29 publications

(22 citation statements)

References 50 publications

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“…Fontinalis mosses in particular have such a key role in boreal streams (Koljonen et al. ) and this was also observed in our experiment where mosses enhanced greatly the retention of both FPOM and CPOM. Thus, organic matter standing stock in moss‐containing streams may be almost an order of magnitude higher than in streams lacking mosses, highlighting the indirect importance of mosses, or macrophytes in general, in fueling detritus‐based stream food webs.…”

Section: Discussionsupporting

confidence: 89%

Combined effects of local habitat, anthropogenic stress, and dispersal on stream ecosystems: a mesocosm experiment

Turunen

Louhi

Mykrä

et al. 2018

Ecological Applications

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The effects of anthropogenic stressors on community structure and ecosystem functioning can be strongly influenced by local habitat structure and dispersal from source communities. Catchment land uses increase the input of fine sediments into stream channels, clogging the interstitial spaces of benthic habitats. Aquatic macrophytes enhance habitat heterogeneity and mediate important ecosystem functions, being thus a key component of habitat structure in many streams. Therefore, the recovery of macrophytes following in-stream habitat modification may be prerequisite for successful stream restoration. Restoration success is also affected by dispersal of organisms from the source community, with potentially the strongest responses in relatively isolated headwater sites that receive a limited amount of dispersing individuals. We used a factorial design in a set of stream mesocosms to study the independent and combined effects of an anthropogenic stressor (sand sedimentation), local habitat (macrophytes, i.e., moss transplants), and enhanced dispersal (two levels: high vs. low) on organic matter retention, algal accrual rate, leaf decomposition, and macroinvertebrate community structure. Overall, all responses were simple additive effects with no interactions between treatments. Sand reduced algal accumulation, total invertebrate density, and density of a few individual taxa. Mosses reduced algal accrual rate and algae-grazing invertebrates, but enhanced organic matter retention and the number of detritus and filter feeders. Mosses also reduced macroinvertebrate diversity by increasing the dominance by a few taxa. Mosses reduced leaf mass loss, possibly because the organic matter retained by mosses provided an additional food source for leaf-shredding invertebrates and thus reduced shredder aggregation into leaf packs. The effect of mosses on macroinvertebrate communities and ecosystem functioning was distinct irrespective of the level of dispersal, suggesting strong environmental control of community structure. The strong environmental control of macroinvertebrate community composition even under enhanced dispersal suggests that re-establishing key habitat features, such as natural stream vegetation, could aid ecosystem recovery in boreal streams.

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Section: Discussionsupporting

confidence: 89%

Combined effects of local habitat, anthropogenic stress, and dispersal on stream ecosystems: a mesocosm experiment

Turunen

Louhi

Mykrä

et al. 2018

Ecological Applications

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“…Increased residence time may alter stream ecosystem functioning by enhancing nutrient uptake and processing of organic matter (Valett et al 1996;Roberts, Mulholland & Houser 2007). Although we did not see any clear benefits from wood additions to aquatic biodiversity, such a long-term effect can be anticipated because LWD reportedly increases stream biodiversity and organic matter retention (Koljonen et al 2012;Pilotto et al 2014), thus helping achieve one of the key goals of most restoration projects, i.e. improved ecological status.…”

Section: Discussionmentioning

confidence: 74%

“…Although we did not see any clear benefits from wood additions to aquatic biodiversity, such a long‐term effect can be anticipated because LWD reportedly increases stream biodiversity and organic matter retention (Koljonen et al . ; Pilotto et al . ), thus helping achieve one of the key goals of most restoration projects, i.e.…”

Section: Discussionmentioning

confidence: 99%

Differential responses by stream and riparian biodiversity to in‐stream restoration of forestry‐impacted streams

Turunen

Aroviita

Marttila

et al. 2017

Journal of Applied Ecology

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Summary Forestry can have detrimental impacts on stream ecosystems, particularly via excessive sedimentation. A key challenge to stream management is therefore to identify the best restoration practices to mitigate the harmful impacts of fine sediments on stream biodiversity and ecosystem functioning. We studied the effects of restoration of sediment‐impacted headwater streams on the habitat structure, hydrologic retention, biodiversity (microbes, bryophytes, benthic macroinvertebrates, riparian plants) and ecosystem functions (periphyton accrual rate and leaf breakdown) by comparing four treatments: wood‐restored, boulder‐restored, impacted (by fine sediments) and near‐natural streams. The restored streams were sampled 3–7 years post‐restoration. Restoration by wooden or boulder structures aimed to reduce deposited sediments and increase channel heterogeneity and hydraulic retention. Wooden structures were ineffective in removing fine bed sediments and did not induce positive responses in aquatic biota. Boulder additions reduced substrate limitation and thereby proved beneficial for aquatic bryophytes. Benthic macroinvertebrates were clearly impaired by sedimentation but responded weakly to restoration. Leaf‐decomposing microbes and ecosystem functions were unresponsive to restoration but neither did they differ between near‐natural and impacted streams, suggesting that they were little harmed by sedimentation. Wood addition enhanced hydraulic retention, and riparian plant assemblages along wood‐restored streams resembled those in near‐natural streams, suggesting that increased retention re‐established a more natural flood regime. By contrast, riparian plant assemblages in boulder‐restored streams did not differ from those in impacted streams. Synthesis and applications. Restoration improved several aspects of stream and/or riparian biodiversity, but had limited effects on ecosystem functions. Different restoration measures resulted in differing biodiversity outcomes: boulder addition was more effective at restoring in‐stream heterogeneity and aquatic biodiversity, whereas wooden structures helped restore channel hydrology and retentiveness, and, consequently, riparian vegetation. Therefore applying both measures in the restoration of forested headwater streams with naturally stony substrates enhances stream habitat variability at the watershed scale, providing the most promising scenario for biodiversity benefits in broad‐scale restoration designs. In‐stream restoration that increases hydraulic retention has impacts that extend beyond ecosystem boundaries, reinforcing the need to restore, manage and protect streams and their riparian forests in an integrated effort.

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“…Integration of this knowledge into restoration planning or design takes the form of adding structure to increase habitat availability. These habitat modifications can play an important role in the restoration process with demonstrated effects in some, but not all, cases (Stewart et al 2009, Louhi et al 2011, Koljonen et al 2012, Palmer et al 2014, Dol edec et al 2015. However, other processes are rarely considered in the design of stream restoration projects even though they may have equally large influences on biodiversity.…”

Section: Introductionmentioning

confidence: 99%

Metacommunity theory meets restoration: isolation may mediate how ecological communities respond to stream restoration

Swan

Brown

2017

Ecological Applications

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An often-cited benefit of river restoration is an increase in biodiversity or shift in composition to more desirable taxa. Yet, hard manipulations of habitat structure often fail to elicit a significant response in terms of biodiversity patterns. In contrast to conventional wisdom, the dispersal of organisms may have as large an influence on biodiversity patterns as environmental conditions. This influence of dispersal may be particularly influential in river networks that are linear branching, or dendritic, and thus constrain most dispersal to the river corridor. As such, some locations in river networks, such as isolated headwaters, are expected to respond less to environmental factors and less by dispersal than more well-connected downstream reaches. We applied this metacommunity framework to study how restoration drives biodiversity patterns in river networks. By comparing assemblage structure in headwater vs. more well-connected mainstem sites, we learned that headwater restoration efforts supported higher biodiversity and exhibited more stable ecological communities compared with adjacent, unrestored reaches. Such differences were not evident in mainstem reaches. Consistent with theory and mounting empirical evidence, we attribute this finding to a relatively higher influence of dispersal-driven factors on assemblage structure in more well-connected, higher order reaches. An implication of this work is that, if biodiversity is to be a goal of restoration activity, such local manipulations of habitat should elicit a more profound response in small, isolated streams than in larger downstream reaches. These results offer another significant finding supporting the notion that restoration activity cannot proceed in isolation of larger-scale, catchment-level degradation.

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Quantifying the effects of in-stream habitat structure and discharge on leaf retention: implications for stream restoration

Cited by 29 publications

References 50 publications

Combined effects of local habitat, anthropogenic stress, and dispersal on stream ecosystems: a mesocosm experiment

Combined effects of local habitat, anthropogenic stress, and dispersal on stream ecosystems: a mesocosm experiment

Differential responses by stream and riparian biodiversity to in‐stream restoration of forestry‐impacted streams

Metacommunity theory meets restoration: isolation may mediate how ecological communities respond to stream restoration

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